1. Field of the Invention
The present invention relates to the field of line threading devices for elongated conduits in general, and in particular to a conduit conforming torpedo construction for accomplishing that objective.
2. Description of Related Art
As can be seen by reference to the following U.S. Pat. Nos. 5,121,644; 5,374,034; 5,499,797; and 5,699,996, the prior art is replete with myriad and diverse systems for threading wire and/or cable through a conduit.
While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, and at least one of them employs a pneumatically inflated cloth parachute, they are uniformly deficient with respect to their failure to provide a simple, efficient, and durable conduit torpedo that will closely conform to the walls of the conduit and employ an air impervious membrane that will reduce the amount of pneumatic pressure required to move the torpedo through the conduit.
As most electricians are aware, one of the most difficult chores that they encounter is the threading of wires and cable through elongated tubular conduits. In addition, while cloth parachutes have been employed in the past to pull an elongated tether along the length of a conduit, this particular approach has a number of significant drawbacks.
To begin with, the non-rigid collapsible nature of the cloth parachute results in many instances in the parachute bell collapsing within the conduit. Once the bell is collapsed, it is difficult, if not impossible to reinflate the bell to propel the parachute any further appreciable distance within the conduit.
In addition, the porous and fragile nature of the parachute material is susceptible to the rupturing of the bell membrane which will either result in the deflation of the bell or require excessively high pneumatic pressure to keep the torn membrane moving through the conduit.
As a consequence of the foregoing situation, there has existed a longstanding need among electricians for a new and improved type of conduit torpedo that is based on a reinforced outwardly biased parachute framework that will conform to the walls of the conduit even when pneumatic pressure is not being employed and the provision of such a construction is a stated objective of the present invention.